Compression ignition engines, for example diesel engines, operate by combustion of fuel and gas mixtures caused by compression of the mixtures, usually within a combustion chamber during a compression stroke. Compression engines offer the advantage of high output power for the amount of fuel used.
The combustion process, however, results in some amounts of emission by-products, such as NOx, HC, soot, and the like, being generated. The amount of emissions may be increased under certain conditions. For example, incomplete mixing of the fuel and gas results in higher temperature regions within the combustion envelope, thus resulting in increased levels of NOx. Higher temperatures overall within the combustion chamber also cause increased amounts of NOx.
Attempts to control various engine parameters and thus reduce emissions have met with limited success. One such strategy which shows promise is the use of homogeneous charge compression ignition (HCCI) technology. HCCI attempts to thoroughly mix the fuel and air within the combustion chamber to provide for uniform combustion temperatures. However, it has proven to be extremely difficult to achieve true HCCI operations and maintain control over the combustion process.
In U.S. Pat. No. 4,860,699, Rocklein discloses a two-cycle engine which delivers a mixture of fuel and air to the combustion chamber through a baffle, i.e., a series of mixing vanes, to promote mixing of the fuel and air. The air is obtained from an accumulator which stores compressed air from some source, such as a crankcase compressor, an external compressor, or a supercharger. The compressed air is always being delivered to the combustion chamber of the two-stroke engine, either to scavenge exhaust gases during the exhaust stroke or to deliver fuel and air during the intake stroke. The fuel is injected into the stream of compressed air prior to entry into the baffle. The fuel and air mixture, however, must be delivered to the combustion chamber for combustion by standard methods, i.e., either spark ignition or compression ignition. Thus, the disclosed engine of Rocklein merely establishes a means to deliver fuel and air to the combustion chamber and does not control combustion in any manner designed to resolve emission issues.
The present invention is directed to overcoming one or more of the problems as set forth above.